Supplementary Information
for
A Recyclable Catalyst That Precipitates at the End of the Reaction
Vladimir K. Dioumaev and R. Morris Bullock*
All manipulations were performed in Schlenk–type glassware on a dual–manifold Schlenk line or in a argon–filled Vacuum Atmospheres glovebox. NMR spectra were obtained on a Bruker Avance 400 FT NMR spectrometer (400 MHz for 1H). All NMR spectra were recorded at 25 °C unless stated otherwise. Chemical shifts for 1H and 13C NMR spectra were referenced using internal solvent resonances and are reported relative to tetramethylsilane. External standards of trifluorotoluene (set as d = –63.73) and 85 % H3PO4 (set as d = 0) were used for referencing 19F and 31P NMR spectra. 13C{1H} and 31P{1H} NMR spectra were recorded with broadband 1H decoupling unless stated otherwise. For quantitative 1H NMR measurements the relaxation delay was set at 30 seconds. GC–MS spectra were recorded on an Agilent Technologies 5973 mass selective detector connected to an Agilent Technologies 6890N gas chromatograph equipped with an HP–5ms column (5 % phenyldimethylpolysiloxane). Infrared spectra were recorded on a Mattson Polaris spectrometer. Elemental analyses were performed by Schwarzkopf Microanalytical Laboratory, Inc. (Woodside, NY).
Hydrocarbon solvents were dried over Na/K–benzophenone. Benzene–d6 was dried over Na/K. Organic carbonyl compounds were dried over CaH2. H2 was used as received. HSiEt3 was dried over LiAlH4. Compounds [CpMo(CO)2(IMes)]+[B(C6F5)4]– and [CpW(CO)2(IMes)]+[B(C6F5)4]– were synthesized as previously reported.1
Turnover number (TON) is the number of moles of a carbonyl substrate consumed to yield a given product and is normalized to the number of moles of catalyst.
Note that each equivalent of an ether (R(R’)HCOCH(R’)R) formed in a hydrosilylation of a ketone (R(R’)C=O) is counted as two turnovers of the catalyst, since it is formed from two equivalents of a ketone. However, each equivalent of an ether (RCH2OR’) formed in a hydrosilylation of an ester (RCO2R’) is counted as one turnover of the catalyst, since it is formed from one equivalent of an ester. Each equivalent of EtOSiEt3 formed in the hydrosilylation of ethyl acetate (MeCO2Et) is counted as 0.5 turnover of the catalyst, since it is formed from 0.5 equivalents of an ester. Total TON is the total number of turnovers for a given product, measured at the end of the reaction.
Synthesis of [CpW(CO)2(IMes)(H)2]+[B(C6F5)4]–. In a glovebox [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (30 mg, 0.022 mmol) was suspended in 10 mL of toluene and placed in a tube equipped with a Teflon valve. The tube was taken out of the glovebox, filled with about 1.1 atm H2 at –196 ˚C, sealed, and warmed to room temperature with vigorous stirring. The colour of the suspension changed almost immediately from brown to yellow. The mother liquor was removed and discarded, and the precipitate was dried in vacuo to yield 26 mg (92 %) of pure [CpW(CO)2(IMes)(H)2]+[B(C6F5)4]– as yellow powder. The sample in THF–d8 was found to contain [CpW(CO)2(IMes)(THF–d8)]+[B(C6F5)4]– and two isomers of [CpW(CO)2(IMes)(H)2]+[B(C6F5)4]–.
major isomer (ca. 85 %). 1H NMR (C6D6) d 6.74 (s, 4H, m–H–Mes), 6.08 (s, 2H, =CH), 4.14 (s, 5H, Cp), 2.13 (s, 6H, p–Me–Mes), 1.62 (s, 12H, o–Me–Mes), –1.11 (br s, 2H, WH). 1H NMR (THF–d8, –30 ˚C) d 7.82 (s, 2H, =CH), 7.17 (s, 4H, m–H–Mes), 5.46 (s, 5H, Cp), 2.37 (s, 6H, p–Me–Mes), 2.06 (s, 12H, o–Me–Mes), –0.7 (br s, n1/2 = 1400 Hz, 2H, WH). 1H NMR (THF–d8, –100 ˚C) d 7.95 (s, 2H, =CH), 7.19 (s, 4H, m–H–Mes), 5.59 (s, 5H, Cp), 2.38 (s, 6H, p–Me–Mes), 2.07 (s, 12H, o–Me–Mes), 1.19 (br s, n1/2 = 13 Hz, 1H, WH), –2.97 (~ br d, n1/2 = 12 Hz, 1JHH = 3 Hz, 1JHW = 34 Hz, 1H, WH). 13C{1H} NMR (THF–d8, –100 ˚C) d 205.2 and 203.1 (s, W–CO), 160.7 (s, NCN), 148.8 (br d, 1JCF = 242 Hz, o–C6F5), 141.0 (br s, p–Mes or i–Mes), 139.0 (dm, 1JCF = 242 Hz, p–C6F5), 138.5 (s, p–Mes or i–Mes), 137.0 (dm, 1JCF = 247 Hz, m–C6F5), 136.4 (br s, o–Mes), 130.6 and 130.5 (s, m–Mes), 127.9 (br s, =CH), 124.5 (br m, i–C6F5), 88.6 (s, Cp), 21.2 (s, p–Me–Mes), 18.7 and 18.3 (s, o–Me–Mes). 19F NMR (THF–d8, –30 ˚C) d –133.5 (d, 8F, 3JFF = 11 Hz, o–C6F5), –164.9 (t, 4F, 3JFF = 21 Hz, p–C6F5), –168.5 (t, 8F, 3JFF = 18 Hz, m–C6F5). minor isomer (ca. 15 %). 1H NMR (C6D6) d 6.57 (br s, 4H, m–H–Mes), 5.97 (br s, 2H, =CH), 3.96 (br s, 5H, Cp), 1.97 (br s, 6H, p–Me–Mes), 1.44 (br s, 12H, o–Me–Mes), –1.25 (br s, 2H, WH2). 1H NMR (THF–d8, –30 ˚C) d 7.76 (br s, 2H, =CH), 5.28 (s, 5H, Cp); other resonances obscured by stronger signals of the major isomer of [CpW(CO)2(IMes)(H)2]+[B(C6F5)4]– and by [CpW(CO)2(IMes)(THF–d8)]+[B(C6F5)4]–.
IR (Nujol) n(CO) = 2073 (vs) and 2018 (vs) cm–1, IR (CF3Ph) n(CO) = 2070 (vs) and 2017 (vs) cm–1, IR (THF–d8) n(CO) = 2005 (vs) cm–1 (second band obscured by solvent), IR (Et2C=O) n(CO) = 2064 (vs) and 2007 (vs) cm–1. Anal. Calcd. for C52H31BF20N2O2W: C, 48.40; H, 2.42; N, 2.17. Found: C, 47.74; H, 2.14; N, 2.00.
Observation of [CpW(CO)2(IMes)(Et2C=O)]+[B(C6F5)4]–. In a glovebox [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (53 mg, 0.038 mmol) and Et2C=O (300 mL, 2.83 mmol) were mixed to produce a dark purple solution and placed in an NMR tube equipped with a Teflon valve. The volatiles were removed in vacuo, and the purple crystalline material was identified as [CpW(CO)2(IMes)(Et2C=O)]+[B(C6F5)4]–.
1H NMR (C6D6) d 6.6 (br s, 4H, m–H–Mes), 6.10 (s, 2H, =CH), 4.49 (s, 5H, Cp), 2.08 (s, 6H, p–Me–Mes), 1.9 (br s, 4H, CH3CH2), 1.70 (br s, 12H, o–Me–Mes), 0.72 (br s, 6H, CH3CH2). 1H NMR (Et2C=O and a sealed capillary of CD2Cl2 for lock, –10 ˚C) d 8.60 (s, 2H, =CH), 7.85 and 7.75 (br s, 4H, m–H–Mes), 5.98 (s, 5H, Cp), 2.71 (br s, 12H, o–Me–Mes), resonances of p–Me–Mes and Et presumably obscured by solvent. 13C{1H} NMR (liquid clathrate, C6D6) d 244.4 (s, W–CO), 239 (br s, Et2C=O), 177 (br s, NCN), 149.4 (dm, 1JCF = 244 Hz, o–C6F5), 141.1 (s, p–Mes or i–Mes; other resonance presumably obscured by signals around 138), 139.2 (dm, 1JCF = 246 Hz, p–C6F5), 137.3 (dm, 1JCF = 246 Hz, m–C6F5), 136.1 (bs s, o–Mes), m–Mes and =CH obscured by solvent at 130–127, 125.4 (br m, i–C6F5), 97 (br s, Cp), 36.6 (br s, CH3CH2), 20.9 (s, p–Me–Mes), 18.0 (br s, o–Me–Mes), 8 (br s, CH3CH2). 13C{1H} NMR (Et2C=O and a sealed capillary of CD2Cl2 for lock, –30 ˚C) d 248.1 and 246.4 (s, W–CO), 241.1 (s, Et2C=O), 177.4 (s, NCN), 148.7 (dm, 1JCF = 244 Hz, o–C6F5), 140.8 (br s, p–Mes or i–Mes), 138.7 (dm, 1JCF = 247 Hz, p–C6F5), 136.9 (s, p–Mes or i–Mes), 136.7 (dm, 1JCF = 247 Hz, m–C6F5), 136.7 (s, o–Mes), 130.2 (s, m–Mes), 128 and 126 (br s, =CH), 124.6 (br m, i–C6F5), 96.0 (s, Cp), 37.8 (s, CH3CH2), 21.0 (s, p–Me–Mes), 18.8, 18.6, and 17.9 (s, o–Me–Mes), 8.9 (s, CH3CH2). 19F NMR d (Et2C=O and a sealed capillary of CD2Cl2 for lock, –30 ˚C) –133.3 (dm, 8F, 3JFF = 11 Hz, o–C6F5), –164.3 (tm, 4F, 3JFF = 21 Hz, p–C6F5), –168.2 (tm, 8F, 3JFF = 17 Hz, m–C6F5). IR (THF) n(CO) = 1963 (vs) and 1863 (vs), n(Et2C=O) = 1718 (w) cm–1. UV(toluene) lmax = 498 nm (e = 1 ´ 103 L mol–1 cm–1).
Synthesis of [CpW(CO)2(IMes)(SiEt3)H]+[B(C6F5)4]–. In a glovebox a solution of HSiEt3 (16 mL, 0.10 mmol) in 0.5 mL of diethyl ether was added to [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (69 mg, 0.050 mmol). The sample was stirred for 10 minutes, and the volatiles were removed in vacuo to yield 70 mg (~100 %) of brown–yellow [CpW(CO)2(IMes)(SiEt3)H]+[B(C6F5)4]–.
major isomer (70 % at 25 ˚C). 1H NMR (C6D6) d 6.74 and 6.69 (s, 2H, m–H–Mes), 6.12 (s, 2H, =CH), 4.64 (s, 5H, Cp), 2.11 (s, 6H, p–Me–Mes), 1.78 and 1.71 (s, 6H, o–Me–Mes), 0.67 (t, 9H, 3JHH = 8 Hz, CH3CH2), 0.31 (dq, 6H, 3JHH = 2 and 8 Hz, CH3CH2), –2.60 (s, 1H, 1JHW = 36 Hz, WH). 13C{1H} NMR (liquid clathrate, C6D6) d 217.2 (br s, CO), 172.3 (s, 1JHW = 134 Hz, NCN), 149.5 (br d, 1JCF = 244 Hz, o–C6F5), 141.0 (s, p–Mes or i–Mes), 139.3 (dm, 1JCF = 250 Hz, p–C6F5), 137.4 (dm, 1JCF = 250 Hz, m–C6F5), 136.9 (s, p–Mes or i–Mes), 135.7 (s, o–Mes), 130.4 (br s, m–Mes), 125.5 (br m, i–C6F5), 125.4 (s, =CH), 92.2 (s, Cp), 21.1 (s, p–Me–Mes), 18.1 (br s, o–Me–Mes), 5.9 (s, CH3CH2), 4.7 (s, 1JCSi = 59 Hz, CH3CH2). 19F NMR d (C6D6) –133.1 (br s, 8F, o–C6F5), –164.1 (t, 4F, 3JFF = 20 Hz, p–C6F5), –167.9 (br s, 8F, m–C6F5). 29Si NMR d (C6D6) 43.2 (s, W–Si). minor isomer (30 % at 25 ˚C). 1H NMR (C6D6) d 6.60 and 6.56 (br s, 2H, m–H–Mes), 6.05 (br s, 2H, =CH), 4.46 (br s, 5H, Cp), 1.99 (br s, 6H, p–Me–Mes), 1.63 and 1.56 (br s, 6H, o–Me–Mes), 0.54 (br t, 9H, 3JHH = 8 Hz, CH3CH2), 0.20 (br q, 6H, 3JHH = 8 Hz, CH3CH2), –2.69 (s, 1H, 1JHW = 36 Hz, WH).
IR (CF3Ph) n(CO) = 1979 (vs) and 1948 (vs) cm–1, IR (liquid clathrate in CH3Ph) n(CO) = 1981 (vs) and 1940 (vs) cm–1. Anal. Calcd. for C58H45BF20N2O2SiW: C, 49.59; H, 3.23; N, 1.99. Found: C, 49.33; H, 3.49; N, 2.06.
Catalytic hydrosilylation of aliphatic ketones with HSiEt3. In a glovebox [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (4 mg, 0.003 mmol), aliphatic ketone (1.50 mmol, 159 mL in case of Et2C=O, or 175 mL in case of CH2=CH(CH2) 2C(O)Me, or 149 mL in case of C3H5C(O)CH3), and HSiEt3 (288 mL, 1.80 mmol) were placed in an NMR tube equipped with a Teflon valve. Two sealed capillaries with C6D6 were placed in the tube for the purpose of NMR lock. The tube was shaken to mix the ingredients, producing a light purple homogeneous solution. The reaction was carried out either at room temperature (~23 °C) or at 53 °C in a constant–temperature bath. The progress of the reaction was periodically monitored by 1H NMR. At high conversions, the polarity of the medium drastically decreased and a purple oil separated from the very light purple solution. When all of the carbonyl substrate was consumed, the solution turned colourless and the oil changed colour from purple to yellow and gradually turned into a solid or a semi–solid.
Determination of catalyst leaching by 19F NMR. In a glovebox [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (4 mg, 0.003 mmol), Et2C=O (1.50 mmol, 159 mL), and HSiEt3 (288 mL, 1.80 mmol) were placed in an NMR tube equipped with a Teflon valve. Two sealed capillaries with a mixture of C6D6 and C6F6 were placed in the tube as internal standards for signal integration and NMR lock. The tube was shaken to mix the ingredients, producing a light purple homogeneous solution. The reaction was left overnight at room temperature (~23 °C). The solubility of catalytic species was detemined by integration of 1H and 19F NMR spectra of the liquid phase of the final heterogeneous system (1H NMR d 8.5-7.5 ppm, 2H, IMes; 19F NMR d -162.9 ppm, 4F, p–C6F5 and –167.8, 8F, m–C6F5) against the internal standards (1H NMR d 7.15, s, residual protons of C6D6; 19F NMR d -162.9, 6F, C6F6) and compared to the results of the similar integration of the signals in the initial homogeneous mixture. The liquid products were then decanted, and a new portion of Et2C=O (1.50 mmol, 159 mL) and HSiEt3 (288 mL, 1.80 mmol) was added. The reaction was left overnight at room temperature (~23 °C), and the quantitative NMR experiments were repeated as described above. The 19F NMR integration in both cases yielded a consistent residual solubility of ~ 4 ´ 10-4 mol L-1 for all species containing B(C6F5)4- counter-ion, which corresponds to a leaching of ~5 % of the loaded 0.2 mol % catalyst. The integration of 1H NMR, on the other hand, yielded no observable species containing IMes ligand, presumably due to a poor sensitivity for the integration of small individual signals of multiple species as compared to the 19F NMR integration of a single collective signal of all B(C6F5)4- containing species.
Catalytic hydrosilylation of Et2C=O with HSiMe2Ph. In a glovebox [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (4 mg, 0.003 mmol), Et2C=O (1.50 mmol, 159 mL), and HSiMe2Ph (280 mL, 1.80 mmol) were placed in an NMR tube equipped with a Teflon valve. Two sealed capillaries with C6D6 were placed in the tube for the purpose of NMR lock. The tube was shaken to mix the ingredients, producing a yellow homogeneous solution. The reaction was carried out at room temperature (~23 °C) and reached completion before the first NMR measurement (< 15 min). The mixture appeared deceptively homogeneous, but small amount of brown oil precipitated after an overnight period.
Catalytic hydrosilylation of aromatic ketones. In a glove box [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (4 mg, 0.003 mmol), aromatic ketone (1.50 mmol, 175 mL in case of PhC(O)Me or 182 mL in case of p–F–C6H4C(O)CH3), HSiEt3 (288 mL, 1.80 mmol), and two sealed capillaries with C6D6 were placed in an NMR tube equipped with a Teflon valve. The reaction was carried out either at room temperature (~23 °C) or at 53 °C in a constant–temperature bath. The progress of the reaction was periodically monitored by 1H NMR. The colour gradually changed from purple to light brown, and small amount of brown oily precipitate was formed.
Determination of the composition of the liquid clathrate formed in the hydrosilylation of PhC(O)Me. In a glove box [CpW(CO)2(IMes)]+[B(C6F5)4]– · CH3Ph (40 mg, 0.030 mmol), PhC(O)Me (1.50 mmol, 175 mL), and HSiEt3 (288 mL, 1.80 mmol) were mixed and placed in a Pasteur pipet sealed at the narrow end. The pipet was capped with a rubber septa and was left at room temperature (~23 °C) inside the glove-box. The colour quickly changed from purple to light brown, and brown oily precipitate was formed in the narrow part of the pipet within ~30 min. The oil proved to be viscous and difficult to transfer from one vessel to another, and the use of a sealed pipet was a convenient way to deliver the oil to the narrow part of the pipet. The system was allowed to equilibrate for another 2 h, and the top liquid phase was removed. The bottom section of the pipet was cut off yielding a capillary filled with brown oil. This capillary and two sealed capillaries with C6D6 were loaded in an NMR tube equipped with a Teflon valve. Note that constraining the oil to a narrow capillary was done primarily for the purpose of better magnetic field homogeneity throughout the sample and therefore, better resolution in the NMR spectra. The composition of the oil was determined by 1H NMR spectroscopy to have ~3.4 equivalents of PhCH(CH3)OSiEt3 per [CpW(CO)2(IMes)H2]+[B(C6F5)4]–.